Thin-film transistors (TFTs) are important components of a drive circuit and are widely applied in display devices. A TFT mainly comprises a gate electrode, an active layer, a source electrode, and a drain electrode; the switching performance of the TFT is degraded if the electrical properties are changed after the active layer is suffered from ultraviolet (UV) irradiation, and the phenomenon is more serious when the active layer is made from a metal oxide with high mobility and good uniformity.
For instance, regarding a polymer light-emitting diode (PLED) display device, the PLED display device comprises an array substrate and a package substrate. As illustrated in FIG. 1, the array substrate comprises a substrate 10 and TFTs and a passivation layer 30 formed on the substrate 10 in sequence; the TFT includes a gate electrode 200, a gate insulating layer 201, an active layer 202, an etch barrier layer 203, a source electrode 205 and a drain electrode 204; and the active layer 202 is made from a metal oxide such as indium gallium zinc oxide (IGZO).
The array substrate of the PLED display device further comprises an emission layer (EML) formed on the substrate. Currently, the EML of the PLED display device is mostly formed through an inkjet printing technology. In order to further optimize the inkjet printing technology, the array substrate is generally cleaned and modified with UV light before the EML is formed. Because a metal oxide has the defect of poor stability due to UV irradiation, when the array substrate is cleaned and modified with UV light, the active layer is subjected to UV irradiation and the electrical properties are changed, so that the switching performance of the TFT is degraded and the TFT even fails, and hence the display performance of the PLED display device can be reduced.